The overall objective of this project is to obtain a better understanding, at the cellular level, of the anatomical and physiological basis of functional interactions between motivation-emotional centers of the brain and motor-behavioral centers of the brain. The proposed studies will focus on the functional interactions between the limbic system and the basal ganglia in the rat brain. Specifically, the nature of basal ganglia neuron circuits involved in processing limbic afferents will be investigated. Since the ventral strio-pallidal system of the basal ganglia receive the bulk of afferent inputs from the limbic system, studies proposed here will determine the synaptic organization of neurons in the ventral strio-pallidal system, and their functional interaction with limbic afferents. The planned studies will use the technique of intracellular recording IN VIVO to analyze physiological properties of neurons in the ventral strio-pallidal system. The nature of afferent inputs from the limbic system will be studied by stimulation of respective limbic nuclei (e.g., amygdala). In addition, we will utilize the technique of intracellular horseradish peroxidase labeling to examine the morphology and the synaptic relationships of the physiologicaly identified neurons, at both the light and the electron microscopic levels. We will also perform studies involving histochemistry and/or immunocytochemistry on tissue containing intracelularly labeled neurons in order to determine the neurochemical properties of the labeled neurons and their synaptic partners. The multidisciplinary studies proposed in this project are unique to the ventral forebrain. The data will enhance our understanding of functional and anatomical properties of neuron circuits in the ventral strio-pallidal system, and the nature of their interactions with the limbic system. The results will be useful in refining present models of basal ganglia functions, and will be necessary for forumulation of both preventive and therapeutic treatments of basal ganglia disorders such as Huntington's Disease and Parkinsonism.